Quantum Transport in Presence of Bound States – Noise Power

The impact of bound states in Landauer‐Büttiker scattering approach to non‐equilibrium quantum transport is investigated. We show that the noise power at frequency ν is sensitive to all bound states with energies ω_b satisfying . We derive the exact expression of the bound state contribution and compare it to the one produced by the scattering states alone. The theoretical and experimental consequences of this result are discussed.     

Molecular dynamics for very large systems on massively parallel computers: The MPSim program

We describe the implementation of the cell multipole method (CMM) in a complete molecular dynamics (MD) simulation program (MPSim) for massively parallel supercomputers. Tests are made of how the program scales with size (linearly) and with number of CPUs (nearly linearly) in applications involving up to 10⁷ particles and up to 500 CPUs. Applications include estimating the surface tension of Ar and calculating the structure of rhinovirus 14 without requiring icosahedral symmetry. © 1997 by John Wiley & Sons, Inc.     

Ir- spectroscopy of hydrogen bond as a method of analytical determination of physical network in poly(ether urethane)s

The equilibrium association of urethane groups in a series of 4, 4′ - diphenylmethane diisocyanate (MDI)/polypropylene oxide) (PPO) based poly(ether urethane) elastomers (PUE) was studied on the basis of IR-spectroscopy data. The concentration of associates containing 2,3 and 4 urethane groups is calculated, which permits immediate monitoring of changes in PUE mechanical properties using the model of a physically cross-linked polymer.     

Nitrogen-Based Linkers with a Mesitylene Core: Synthesis and Characterization

Mesitylene was used as a core in seven new tritopic nitrogen containing linkers. Three of the linkers, each containing three nitrile groups, were obtained through Suzuki, Sonogashira and Heck-type coupling reactions. Next, these were converted to tetrazol-5-yl moieties by the cycloaddition of sodium azide to the nitrile functionalities. The last linker, containing three 1,2,3-triazol-4-yl moieties, was synthesized by the Huisgen cycloaddition of phenyl azide to the corresponding alkyne. The latter was obtained via a Corey–Fuchs reaction sequence from the previously reported formyl derivative. As the proof of concept for their potential in MOF design, one of the nitriles was used to build an Ag-based network.     

VIP-2 —High-Sensitivity Tests on the Pauli Exclusion Principle for Electrons

The VIP collaboration is performing high sensitivity tests of the Pauli Exclusion Principle for electrons in the extremely low cosmic background environment of the underground Gran Sasso National Laboratory INFN (Italy). In particular, the VIP-2 Open Systems experiment was conceived to put strong constraints on those Pauli Exclusion Principle violation models which respect the so-called Messiah–Greenberg superselection rule. The experimental technique consists of introducing a direct current in a copper conductor, and searching for the X-rays emission coming from a forbidden atomic transition from the L shell to the K shell of copper when the K shell is already occupied by two electrons. The analysis of the first three months of collected data (in 2018) is presented. The obtained result represents the best bound on the Pauli Exclusion Principle violation probability which fulfills the Messiah–Greenberg rule.     

Longitudinal Patent Analysis for Nanoscale Science and Engineering: Country,Institution and Technology Field

Nanoscale science and engineering (NSE) and related areas have seen rapid growth in recent years. The speed and scope of development in the field have made it essential for researchers to be informed on the progress across different laboratories, companies, industries and countries. In this project, we experimented with several analysis and visualization techniques on NSE-related United States patent documents to support various knowledge tasks. This paper presents results on the basic analysis of nanotechnology patents between 1976 and 2002, content map analysis and citation network analysis. The data have been obtained on individual countries, institutions and technology fields. The top 10 countries with the largest number of nanotechnology patents are the United States, Japan, France, the United Kingdom, Taiwan, Korea, the Netherlands, Switzerland, Italy and Australia. The fastest growth in the last 5 years has been in chemical and pharmaceutical fields, followed by semiconductor devices. The results demonstrate potential of information-based discovery and visualization technologies to capture knowledge regarding nanotechnology performance, transfer of knowledge and trends of development through analyzing the patent documents.     

Self-organized heteroditopic macrocyclic superstructures

[structure: see text] The synthesis of heteroditopic macrocyclic ureido receptors and of their NaX complexes is described. NMR studies and determination of the crystal structure show the formation of self-organized dimeric or polymeric superstructures by a cooperative macrocyclic cation complexation, anion-hydrogen bonding, and pi-pi stacking interactions. Membrane transport experiments show a direct relation between the synergetic ion-pair recognition and the transport properties of these molecular information transfer devices.     

Silver(I) coordination polymers containing heteroditopic ureidopyridine ligands: the role of ligand isomerism, hydrogen bonding, and stacking interactions

New silver (I) coordination polymers has been successfully designed and synthesized using heteroditopic ureidopyridine ligands 1 and 2 via a combination of coordinations bonds, hydrogen bonding, and pi-pi stacking interactions. This study shows an example of the orientation of the pyridine nitrogen relative to the urea moiety (4-substituted, 1, or 3-substituted, 2), used to control the packing of resulting crystalline coordination polymers. The ureidopyridine ligands present some flexibility because of the conformational rotation around the central urea moiety. The co-complexation of the silver(I) cation by two pyridine moieties and of the PF(6)(-) counteranion by the urea moiety results in the formation of discrete [1(2)Ag](+)PF(6)(-), (3) and [2(2)Ag](+)PF(6)(-), (4) complexes presenting restricted rotation around the central urea functionality. The geometrical information contained in the structures of ligands 1 and 2 and the heteroditopic complexation of silver hexafluorophosphate are fully exploited in an independent manner resulting in the emergence of quasi-rigidly preorganized linear and angular building blocks of 3 and 4, respectively. Additional pi-pi stacking contacts involving interactions between the pi-donor benzene and the pi-acceptor pyridine systems reinforce and direct the self-assembly of the above-described combined structural motifs in the solid state. Accordingly, linear and tubular arrays of pi-pi stacked architectures are generated in the solid state by synergistic and sequential metal ion complexation, hydrogen bonding, and pi-pi stacking interactions.     

The Reaction of Dihalocarbenes with Quadricyclane

The reactions of difluoro-, dichloro- and dibromocarbene with quadricyclane ( 2 ) were examined. In all cases, conversions were low (4–15%), but three distinct reaction courses were observed: cleavage, 1,2-addition, and 1,4-addition. Difluorocarbene gave mainly 6-endo-(2,2-difluorovinyl)-cis-bicyclo[3.1.0]hex-2-ene ( 8 ; 52–89% relative yield), together with minor amounts of exo-3,3-difluorotricyclo[3.2.1.0^2,4]oct-6-ene (7; 13–17%), and 4,4-difluorotetracyclo[3.3.0.0^2,8.0^3,6]octane ( 5 ; 2–4%). Dichlorocarbene gave analogous products, but in relative yields of 35 ( 17 ), 51 ( 11 ), and 12% ( 16 ). The product 11 of 1,2-endo addition underwent further rearrangement to its allylic derivative 12 . A small amount of 1,2-endo addition also occurred (2% of 14 / 15 ). Dibromocarbene gave predominantly products derived from rearrangement of the 1,2-exo (61% of 20 / 21 ) and 1,2-endo adducts (10% of 23 / 24 ). In addition, a significant amount of 4,4-dibromotetracyclo[3.3.0.0^2,8.0^3,6]octane ( 25 ; 21%) was formed. The cleavage product, 6-endo-(2,2-dibromovinyl)-cis-bicyclo[3.1.0]hex-2-ene ( 26 ) was also observed (7%). The yields and product compositions were compared to those obtained from norbornadiene ( 1 ) and found to be entirely different (Table 1), for example no cleavage occurred with difluorocarbene.     

Self-assembly,structure, and dynamic interconversion of metallosupramolecular architectures generated by Pb(II) binding-induced unfolding of a helical ligand

The binding of lead(II) cations to the terpyridine-type subunits of the helical ligand 1 leads to the self-assembly of different polynuclear metallosupramolecular architectures of nanometric size. Three different entities are generated and may be interconverted as a function of metal/ligand stoichiometry: a [4 x 4]Pb(16)(II) grid-type array 2, a [4 # 4]Pb(12)(II) double-cross species 4, and an intermediate complex 3. The structures of 2 and 4 have been confirmed by X-ray crystallography; that of 3 is based on NMR spectral data. The interconversion of the three species generates dynamic diversity and represents an expression of constitutional dynamic chemistry. In the course of ion binding, the helical molecules of ligand 1 unwrap to yield fully extended strands arranged in perpendicular fashion in the architectures 2-4 generated. This process amounts to molecular motions in two directions which confer to the present systems characteristics of two-dimensional nanomechanical devices, capable of performing 2D-contraction/extension motions. The triple features of self-organization, dynamic interconversion, and potential addressability displayed by the processes described trace a self-fabrication approach to nanoscience and nanotechnology.